This article looks at the discourses regarding Nigerian confraternities’ expansion to Europe. It analyses how networks of individuals working together for solidarity, economic or political objectives became categorized as organised crime or as a mafia. I use original data and police investigations, interviews with members and victims, judges, police officers, and journalists to show how the work of French and Italian institutions led to the emergence and transformation of discourses regarding the “Nigerian mafia” which, in the context of the 2015 migration crisis, came to designate confraternities. The circulation of these categories and frames cannot only be accounted for by the work of state institutions, but needs to be analysed through the sociology of information production and practices, which explains the effects of circular reporting, imposition of frames and narratives coming directly from investigations on criminal issues instead of other approaches to Nigerian migration.